Prevented Plant Provides Opportunity to Experiment with Cover Crops

July 1, 2019

Question: What advice do you have for those of us taking prevented plant on some acres this year that have never experimented with cover crops?

Answer: “Prevented plant” acres provide a great opportunity for farmers that haven’t planted cover crops in the past to do some experimenting, said Roger Zylstra, farmer from Jasper County. “Planting cereal rye, radishes, turnips and maybe even some rapeseed in July provides the crop with an excellent chance for good results,” he said.

Mark Heckman, a farmer from Muscatine County agrees and encourages farmers to focus on the task they hope to accomplish. “In my case, I want to suppress weeds and retain nutrients,” he said. “Where I have prevented plant acres, I am looking at a mix of rye for weed suppression and to hold soil structure and will add radishes to hold the nutrients.”

Heckman says this fall, the radishes will die and the rye will come back next spring.

Doug Adams, a farmer from Humboldt County encourages farmers that applied nitrogen to plant a cover crop because it will leach away if not used by a crop. “That cover crop taking up the nitrogen can return it to the soil,” he said.

“I’d lean towards a grass-based cover crop like oats, wheat or cereal rye, as the residue from those crops is easy to handle,” added Adams. “Growing something like sorghum might have a greater need for nitrogen and will grow more biomass, but it may be intimidating when thinking of planting something into that residue next spring. However, if terminated early and allowed to break down yet this year, it would act like cornstalks.”

Adams says farmers need to consider their crop rotation plans for 2020 when selecting a cover crop. “Selecting a cover crop that will complement the cash crop next spring is ideal. If going to corn, consider planting a legume that can generate some nitrogen this summer like cowpeas or some type of clover. If going to soybeans in 2020, I’d try to plant a higher residue-type crop this summer because we need to keep the soil covered to reduce erosion.”

Additionally, Adams says if any herbicides were applied to the prevented plant field, cover crops should be planted in test blocks. He says 3-by-3-foot test blocks work well to determine if the herbicide will affect the growth of the cover crop. “If just grown for a cover crop, we don’t need to worry a lot about herbicide label restrictions, but if use for grazing/haying, then follow the label,” he advises.

“Planting a multispecies cover crop mix is always better. With our corn and soybean rotation here in Iowa, this may be the only chance to fit many of these species into our system,” said Adams. “While many producers will look for the cheapest cover crop option, they need to look at it as an insurance policy that will hold on to the nutrients and soil on their farm. Since 2019 hasn’t gone as planned, I’d like farmers to plan for a successful 2020.”

Adams encourages farmers to discuss their options with their NRCS office or local SWCD commissioners.

The Iowa NRCS has developed a guide with suggested cover crops and seeding rates for cover crops on prevented plant acres. Click here.